The Pharmaceutical Journal
Vol 270 No 7233 p104
25 January 2003

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Journal of the National Cancer Institute (jncicancerspectrum.oupjournals.org)

Chemopreventive effect of tamoxifen confirmed

An updated analysis of a European study supports the use of tamoxifen for prevention of breast cancer in women at high risk for oestrogen receptor (ER) positive disease.

The Italian randomised trial of tamoxifen now includes over six years' follow up of 5,408 women who had undergone hysterectomy and were assigned to either tamoxifen 20mg per day or placebo.

In contrast with earlier analyses, the latest data indicated an 82 per cent risk reduction in 702 women at high risk of hormone-dependent disease (15 cases in the placebo group and three cases in the tamoxifen group, P=0.03). Women in this group were deemed at high risk because of factors including starting menstruation at or before the age of 13, not having had children before 24 and being taller than 160cm. There was also a statistically significant difference in favour of tamoxifen in high risk women who had used hormone replacement therapy.

The authors note that, if these findings can be confirmed, it may be possible to target tamoxifen use for breast cancer prevention to women most likely to benefit from the drug. Because of an association with increased risk of endometrial cancer and venous thromboembolic events, the drug is not recommended as a preventive agent for the general population (Journal of the National Cancer Institute 2003;95:160).

In an accompanying editorial, doctors from the University of Pittsburgh school of medicine say: "What remains unknown is whether this demonstrated reduction in the incidence of breast cancer will ultimately lead to an increased survival or overall health benefit for women at risk, or whether women previously taking HRT should consider tamoxifen for prevention.

"Identifying women who are likely to develop ER-positive breast cancer is important when attempting to maximise the net benefits of tamoxifen use, but using tamoxifen combined with HRT is not recommended outside of a clinical trial setting."

They suggest that newer agents, such as raloxifene and aromatase inhibitors, which are being evaluated for breast cancer risk reduction in trials, may be effective without increasing the risk of uterine cancer. "Continued follow up of the patients in these trials will help to answer these questions in the near future," they add.